Hi,
I would suggest that puppy classes can do more harm than good if they are trying anything other than socialising. I would never take a dog that didn't know at least how to walk on the lead, sit and come to any training class. It is asking an awful lot of a raw dog to learn under such extreme distraction.
If you ever go to a class and are spoken to in that manner again say quite clearly, "I don't know the best way to train my dog and that is why I am here. I am paying you to teach me and I don't learn very well when I am spoken to like that as it upsets me. Could we please start this excersise again?" Dog trainers who have such a superior attitude are not used to being challenged and as long as you are calm this will either sort out the problem or confirm that it is not the right class for you.
A friend of mine had a similar experience and asked me to come to the class and see what I thought. During a break I suggested the next time the instructor spoke to her that way she should speak up. She did and the instructor shouted that only my friend felt that way and was disrupting the class. The rest of the class then spoke up and said they all felt the same!
The following week the instructor apologised to them all and many happy years were then spent by my friend in the class.